Power and/or Alarming Security System for Electrical Appliances

ABSTRACT

The present disclosure relates generally to security systems and, more particularly, to a power and/or alarming security system for electrical appliances. In an example embodiment, an apparatus comprises a socket and a circuit. The socket can be configured for detachable electrical connection with an electrical appliance. The circuit can be configured to (1) provide power to a connected electrical appliance through the socket, and (2) calibrate an alarm limit for a security function for the socket based on a plurality of electrical characteristics of the connected electrical appliance that are measured via the socket, wherein the electrical characteristics comprise an admittance characteristic and a current draw characteristic of the connected electrical appliance. Furthermore, the circuit can calibrate the alarm limit for the socket according to a plurality of calibration phases.

CROSS-REFERENCE AND PRIORITY CLAIM TO RELATED APPLICATIONS

This patent application is a continuation of U.S. patent applicationSer. No. 16/117,304, filed Aug. 30, 2018, and entitled “Power and/orAlarming Security System for Electrical Appliances”, now U.S. Pat. No.______, which claims priority to (1) U.S. provisional patent application62/651,598, filed Apr. 2, 2018, and entitled “Power and/or AlarmingSecurity System for Electrical Appliances”, and (2) U.S. provisionalpatent application 62/553,770, filed Sep. 1, 2017, and entitled “Powerand/or Alarming Security System for Electrical Appliances”, the entiredisclosures of each of which are incorporated herein by reference.

INTRODUCTION

In many environments, such as retail store environments, it is desirableto reduce the risk of theft with respect to electrical appliances. Forexample, in many retail stores, electrical appliances are on display tocustomers in a manner that allows a customer to hold and operate suchappliances as this can help customers make purchase decisions about theelectrical appliances. However, many conventional loss preventionsystems in the art for electrical appliances can be obstructive withrespect to the degree of customer interactions that are permitted withthe displayed electrical appliances. To provide loss prevention securitywhile still permitting a high degree of customer interaction, theinventors disclose how security functions for the electrical appliancescan be integrated into a power strip for the electrical appliance. Sucha “smart” or “intelligent” power strip can be designed to not onlyprovide power to a connected electrical appliance but also trigger analarm if the electrical appliance is disconnected from the power strip.Such an intelligent power strip can include one or more sockets throughwhich an electrical appliance is connected. The power strip can monitorelectrical characteristics of the connected electrical appliance throughthe socket and make decisions based on these monitored electricalcharacteristics as to whether an alarm should be triggered.

However, there are a variety of technical challenges with respect to howto design such a power strip so that the risk of false alarms is reducedwhile still providing adequate security. For example, it is desirable toallow customers to operate a connected electrical appliance so that thecustomer can make a purchase decision. Such operation may cause widevariances in the electrical characteristics of the connected electricalappliance (e.g., the current drawn through the socket may vary based onthe nature of use and whether the electrical appliance has been turnedon or off by a user). As an example, if the connected electricalappliance is a lamp, it is desirable for the power strip to not triggeran alarm in response to a customer action of turning the lamp on andoff. Instead, the alarm should be triggered in response to a persondisconnecting the lamp from the power strip. The inventors disclose avariety of solutions for distinguishing between such actions through themonitored electrical characteristics.

Furthermore, different electrical appliances can have vastly differentelectrical characteristics when connected to a power strip (e.g., lampsversus TVs versus vacuum cleaners, etc.). Further still, it is desirablefor the power strip to provide security functions for not onlyelectrical appliances that receive and operate from AC power but alsofor electrical appliances that receive and operate from DC power. Thereare additional technical challenges in designing an intelligent powerstrip that is able to accommodate and work with such a wide array ofdifferent types of electrical appliances, and the inventors disclose avariety of solutions to this problem as well.

These and other features and advantages of the present invention will bedescribed hereinafter to those having ordinary skill in the art.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A shows an example embodiment of various intelligent power stripsthat include a security function as described herein.

FIG. 1B shows top, side, and bottom views of an example power strip.

FIG. 1C shows an example system diagram of an example power strip.

FIG. 2 shows an example admittance and current sensor circuit.

FIG. 3 shows an example graphical view of the sensors of a power stripagainst a pseudo noise modulated signal according to an exampleembodiment.

FIG. 4 shows an example graphical view of actual impedance measurementsobtained by a power strip over multiple frequencies compared againstideal impedance measurements according to an example embodiment.

FIG. 5A shows an example calibration process flow.

FIG. 5B shows an example categorization and alarm limit setting processflow.

FIG. 6 shows another example categorization process flow.

FIG. 7 shows another example calibration process flow.

FIG. 8 shows another example calibration process flow.

FIG. 9 shows an example calibration and monitoring process flow.

FIG. 10 shows an example perspective view of a power strip connectedwith an expansion module according to an example embodiment.

FIG. 11 show multiple examples of perspective views of an expansionmodule according to an example embodiment.

FIG. 12 is an example perspective view of the power strip connected tothe expansion module with external appliances lined up to be connectedto the front input ports of the expansion module according to an exampleembodiment.

FIG. 13 shows another example embodiment of an expansion module arrangedas a remote access unit according to an example embodiment.

FIG. 14 shows a standalone view of an example remote access unitaccording to an example embodiment.

FIG. 15 is a perspective view of an example remote access unit showing anotification functionality according to an example embodiment.

FIG. 16 is a back view of an example remote access unit according to anexample embodiment.

FIG. 17 shows an example embodiment where a power strip offloadscalibration and/or monitoring functions to a remote computer system viawireless connectivity with the remote computer system.

FIG. 18 shows an example embodiment where secured sockets are includedas part of a wall outlet.

Reference is made in the following detailed description to accompanyingdrawings, which form a part hereof, wherein like numerals may designatelike parts throughout that are corresponding and/or analogous. It willbe appreciated that the figures have not necessarily been drawn toscale, such as for simplicity and/or clarity of illustration. Forexample, dimensions of some aspects may be exaggerated relative toothers. Further, it is to be understood that other embodiments may beutilized.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

References throughout this specification to one implementation, animplementation, one embodiment, an embodiment and/or the like means thata particular feature, structure, and/or characteristic described inconnection with a particular implementation and/or embodiment isincluded in at least one implementation and/or embodiment of thedisclosure. Thus, appearances of such phrases, for example, in variousplaces throughout this specification are not necessarily intended torefer to the same implementation or to any one particular implementationdescribed. Furthermore, it is to be understood that particular features,structures, and/or characteristics described are capable of beingcombined in various ways in one or more implementations and, therefore,are within intended claim scope. In general, these and other issues varywith context. Therefore, particular context of description and/or usageprovides helpful guidance regarding inferences to be drawn.

As will be described in greater detail below, in an implementation, apower and/or alarming security system (e.g., a power strip, etc.) forelectrical appliances may be utilized to facilitate and/or support lossprevention that may provide power to and/or secure multiple electricalappliances. FIG. 1A shows example embodiments of intelligent powerstrips 100 that provide a security function for connected electricalappliances. Any of a wide variety of electrical appliances can beconnected to the power strip 100 in example embodiments. For example,electrical appliances that operate from AC power may be used (e.g.,vacuum cleaners, televisions, lamps, etc.). As another example,electrical appliances that operate from DC power may also be used (e.g.,laptop computers, tablet computers, smart phones, etc.). For ease ofreference, the terms “electrical appliance” and “electrical device” or“device” will be used interchangeably in the context of items connectedto a system socket. In a retail store context, such appliances/devicescan also be referred to as SKUs. However, it should be understood thatthe devices secured by example embodiments described herein need notnecessarily be items for retail merchandising. But, at the same time, itshould be understood that the power strips 100 can be used to providepower and security for a plurality of electrical appliances that aremerchandised to customers in a store. In the example of FIG. 1A, eachpower strip 100 includes 6 sockets 102 into which electrical appliancescan be plugged to form an electrical connection between circuitry in thepower strip 100 and the electrical appliance. While the example of FIG.1A shows each power strip including 6 sockets 102, it should beunderstood that the power strip 100 may comprise more or fewer sockets102 if desired by a practitioner. Accordingly, the power strip 100 maycomprise one or more sockets 102 depending upon the desires of apractitioner. FIG. 1A also shows that the socket configurations (e.g.,plug/pin layout) may vary by geographic region to comply with socketstandardization in those regions. As such, the sockets 102 may vary interms of the shape and plug/pin configurations by regions as indicatedby FIG. 1A. Further still, the nature of the power signal itself mayalso vary by region. FIG. 1B shows top, bottom, and side views of anexample power strip 100 from FIG. 1A.

FIG. 1C shows a high-level system block diagram for an example powerstrip 100. In this example, the power strip 100 includes a circuit thatallows the power strip 100 to continuously and/or periodically measureelectrical characteristics of the electrical appliances connected to thesockets 102. The power strip 100 may enunciate an alarm or other type ofindication if these characteristics deviate significantly from their setpoints. As examples, the measured electrical characteristics may includeadmittance characteristics of the connected electrical appliances and/orcurrent draw characteristics of the connected electrical appliances.Such activities can be performed on a per-socket basis so that alarmscan be independently triggered for each socket 102.

The example power strip 100 of FIG. 1C includes a current/admittancesensor circuit 110 connected to each socket 102. These circuits 110 cansense the admittance and current draw characteristics of a connectedelectrical appliance through each socket 102. The power strip 100 mayalso include one or more processors for processing the sensed admittanceand current draw characteristics to make decisions about how to setalarm thresholds and monitor for alarm triggers. For example, ameasurement processor 112 can process the sensed admittance and currentdraw characteristics to compute a plurality of data values thatrepresent the sensed admittance and current draw characteristics. Itshould be understood that these computed values need not be precisemeasurements such as admittance in units of Siemens. Instead, thecomputed values need only be indicative of the admittance and/or currentdraw characteristics of the connected appliances. The measurementprocessor 112 may include an analog to digital converter (ADC) 116 and adigital signal processor (DSP) such as a field programmable gate array(FPGA) 114 that performs computations on the digitized admittance andcurrent draw signals. Also, a processor 120 such as a CPU ormicrocontroller unit (MCU) can process the computed measurements fromthe measurement processor 112 can make decisions about how to set alarmthresholds and whether to trigger alarms based on these thresholds.Processor 120 can be programmed with a plurality of processor-executableinstructions that can be stored in a non-transitory computer-readablestorage medium such as a memory accessible to processor 120.

The power strip 100 of FIG. 1C may also include a surge protectorcircuit 122 that provides surge protection that is in-line with incomingpower received via plug 124 from a wall outlet or the like that providesthe power strip 100 with a source of AC power. The power strip 100 mayalso include a switch 126 that is operable to connect/disconnect thesockets 102 to/from the incoming power.

Processor 120 may be in communication with an interface 130 throughwhich credentials for authorized users are received (to facilitatecontrol decisions such as arming, disarming, and/or calibrating thepower strip 100). Examples of techniques that can be used forwhitelisting authorized users and authenticating authorized users aredescribed in U.S. Pat. No. 9,892,604 and U.S. Pat. App. Pub.2017/0300721, the entire disclosures of which are incorporated herein byreference. Processor 120 may also be in communication with a piezoelement 132 such as a speaker that can enunciate an alarm if theprocessor determines that an alarm security condition is present.Processor 120 may also be in communication with one or more statusindicators (e.g, LEDs) that provide a visual indication of anoperational status for the power strip (e.g., armed, disarmed, alarming,etc.).

The processor 120 may also be in communication with an expansion port136 via an isolation circuit 138. The expansion port 136 can provideconnectivity for the power strip 100 with a number of peripheraldevices, examples of which are discussed below.

It should be understood that the power strip 100 shown by FIG. 1C is anexample, and the power strip 100 may include more or fewer componentsthan shown by FIG. 1C. For example, if a practitioner chooses not toprovide for an expansion capability, the expansion port 136 andisolation circuit 138 may be omitted. As another example, anotherpractitioner may choose to consolidate the processing capabilities ofprocessors 112 and 120 into a single processor. As yet another example,any of interface 130, piezo element 132, and/or status indicators 134may be omitted if desired by a practitioner. Further still, if apractitioner wants to permit the power strip 100 to wirelesslycommunicate with remote computer systems, the strip 100 may also includea wireless transceiver or the like to provide connectivity with awireless network. Such a wireless transceiver can permit the power stripto serve as a wireless node in a wirelessly connected environment suchas that described by US Pat. App. Pub. 2017/0164314, U.S. provisionalpatent application Ser. No. 62/650,992, filed Mar. 30, 2018 and entitled“Wirelessly Connected Environment of Wireless Nodes”, U.S. patentapplication Ser. No. 16/001,601, filed Jun. 6, 2018 and entitled“Location Tracking of Products and Product Display Assemblies in aWirelessly Connected Environment”, published as US Pat. App. Pub.2018/0288720, U.S. patent application Ser. No. 16/001,605, filed Jun. 6,2018 and entitled “Remote Monitoring and Control over Wireless Nodes ina Wirelessly Connected Environment”, published as US Pat. App. Pub.2018/0288721, and U.S. patent application Ser. No. 16/001,631, filedJun. 6, 2018 and entitled “Wirelessly Connected Hybrid Environment ofDifferent Types of Wireless Nodes”, published as US Pat. App. Pub.2018/0288722, the entire disclosures of which are incorporated herein byreference. Through such wireless connectivity, the power strip 100 canbe remotely monitored and controlled (e.g., by delivering notificationsabout alarms to responsible personnel via messaging to portablecomputing devices and the like, by remotely arming/disarming powerstrips (or individual sockets 102 within the power strip 100) inresponse to commands from the remote computer system, etc.). Still othervariations are possible.

In order to control the security function of the power strip 100 inexample embodiments, two basic phases of operation occur. A first phasecomprises a calibration phase, and a second phase may comprise amonitoring phase. During the calibration phase, for example, the systemmay characterize the device attached to each socket to determine thegeneral current and/or admittance characteristics of the device so thatan appropriate alarm threshold can be determined for each device. Aftereach device has been characterized and the alarm criteria and/orthresholds have been determined, the monitoring phase is entered. In themonitoring phase, the same circuits are used to continuously orregularly monitor each socket 102 for changes and/or trigger an alarm ifthe limits set in the calibration phase are exceeded.

In an example embodiment, the power strip 100 (which may described as a“Sell Plug” or “Secure Plug”) uses two distinctly different types ofmeasurements that it performs in both the calibration and/or monitoringphases of operation. These different measurements may be currentmeasurement and/or admittance measurement. The admittance measurementmay be to determine the length of the cable used by the device toconnect with socket 102 and the type of load represented by the deviceconnected to that cable. The current measurement may be used todetermine the real part of the current drawn by the device. By lookingat and/or examining how these two parameters vary under multiplespecified conditions during the calibration phase, the type of deviceconnected to socket 102 can be determined. Once the type of device hasbeen determined, the alarm criteria may be set accordingly to therebycustomize the alarm criteria to the device that is connected to socket102.

FIG. 2 shows an example embodiment of a current/admittance sensorcircuit 110 that can be employed by the power strip 100 to senseadmittance and current draw through a socket 102. As shown by FIG. 1C,there may be a single sensor circuit 110 for each socket 102 of thepower strip 100. In an example embodiment, the sensor circuit 110 maycomprise an analog circuit that stimulates the device on itscorresponding socket 102, and/or amplifies the response received so thatthe response can be converted to the digital domain and/or processed.

In some embodiments, the sensor circuit 110 may measure admittance bygenerating stimulation signals at a plurality of different frequencies(e.g., 12 different frequencies, although a different number offrequencies may be used if desired by a practitioner), and/or byrecording the response from the socket 102 at each of these twelvefrequencies. This stimulation signal may comprise differential analogsignals that may be generated by a digital signal processor (DSP) suchas FPGA 114. When applied to the bases of transistors Q4 and/or Q5 (asseen in FIG. 2), transistors Q4 and/or Q5 make up a modified bridgecircuit along with resistors R11, R12, R14, and R15. An input signal maybe buffered by followers Q4 and/or Q5. The input signal may be presentedto a fixed inductance, for example 22 micro-Henry, load on one side, anda variable inductance, for example 22 micro-Henry, load in parallel withthe neutral wire of the external cable connected to the socket load. Aresulting signal is summed at the emitter of transistor Q1. Theresulting signal represents the difference in admittance between thefixed inductor and the variable inductor resulting from the parallelcombination of the fixed, for example, 22 micro-Henry inductor and thecable load. This difference represents the admittance of the cable atthat frequency. By performing a differential measurement, any noise onthe input signal may be nulled out because it is common to both sidesand is therefore not part of the differential result. The summed signalis amplified by common base amplifier Q1 with a snubber circuit on theoutput to reduce ringing at the resonant frequency of the inductors.Additional gain is provided by emitter degenerated common emitteramplifier Q3. The output of Q3 is presented to the ADC 116 forconversion into a digital signal. Operational amplifier U1 providesfeedback around the two gain stages to keep the system biased to a pointhalf way between optimization for the ADC (analog-to-digital) input. Thesignal is digitized at 100 MHz, and the digital representation is thenprocessed by the DSP FPGA 114.

As noted, in an example embodiments, the admittance can be measured at12 different frequencies. Two frequencies per octave can be used. Thesefrequencies can be integer divides of the 100 MHz clock. The divideratios may comprise 2, 3, 4, 6, 8, 12, 16, 24, 32, 48, and/or 64. Thisprovides frequency coverage between 1.5 MHz and 50 MHz. All frequenciesare run sequentially through each socket. The total time to measure allfrequencies on each socket is approximately 6 ms. The stimulus and/orresponse are both controlled by the DSP FPGA 114 so that the phase ofthe response relative to the stimulus is also known. Both the amplitudeand phase of the response are used by the FPGA 114 to determine theadmittance at a given frequency.

In example embodiments, the sensor circuit 110 can also be used tomeasure the current. The current can measured across a sense resistorR24 which is in series with the neutral line of the socket. ResistorsR25 and/or R26 set the gain to amplifier U1 which multiplies the resultup to the appropriate input level for the ADC with the help oftransistor amplifiers Q1 and/or Q3.

The current measurement circuit can be triggered by the FPGA 114 at aknown phase with the AC line. The FPGA 114 makes a series ofmeasurements at precise times for 100 ms. These measurements captureboth the magnitude and the phase of the current so that reactive and/orresistive loads can be differentiated. The raw measurements arecorrected for known phase delays in the circuit to present an accuraterepresentation of the magnitude and/or phase of the current drawn by thedevice connected to the socket 102.

In some embodiments, the FPGA 114 is responsible for generating stimulusto the sensor circuit 110 and/or processing the response received backfrom the sensor circuits 110. The FPGA 114 is advantageous as a computeresource for processing the signals from sensor circuits 110 because theFPGA 114 provides faster performance relative to a conventionalmicrocontroller or the like while providing more flexibility than anapplication-specific integrated circuit (ASIC) because the FPGA can bere-configured in the field post-manufacture, thereby allowingpractitioners to upgrade and/or modify the processing logic implementedby the FPGA 114 over time. The faster performance can be advantageous inreducing the time needed to process signals used as part of thecalibration and monitoring processes, which can minimize undesirabledelays in these processes. Functions can be implemented on the FPGA 114in synthesizable RTL (register-transfer level) code.

In example embodiments, admittance testing can performed with themeasurement processor 112. To perform admittance testing, themeasurement processor 112 generates each of the twelve measurementfrequencies via integer divide of the 100 MHz DSP clock. The measurementprocessor 112 also generates a pseudo noise (PN) sequence. This is aseries of ones and/or zeros generated by a linear feedback shiftregister. Each frequency is then modulated by this PN sequence to spreadthe spectrum of the injected signal to prevent it from radiating inviolation of emission standards. This modulated PN sequence may then besent to the sensor circuits 110.

FIG. 3 illustrates correlation in response from the sensors against thepseudo noise modulated signal that may be conveyed to the sensors toextract cable admittance characteristics from one or more sensoroutputs. The correlation function aligns the phase of the two signals(stimulus and/or response) such that both magnitude and/or phaseinformation can now be extracted from the response. Since the responsewas the difference in response of the cable to the response of a knownload on the other side of the sensor, the result is a fairly accuraterepresentation of the real and imaginary reactance of the load on thesocket. Absolute accuracy is not critical as all that is required is theability to sense a change that is representative of the removal ormodification of the load on a socket. In example embodiments, the designtarget is about 5 Ohms of impedance or less than 1 inch of cable lengthchange. This accuracy is limited by parasitics, such as parasiticcapacitances and/or inductances in the system, but performs andacceptable job of measuring complex admittance across frequency.

FIG. 4 illustrates an example of actual impedance measurements overmultiple frequencies compared against ideal impendence measurement. Asstated above, admittance measurements are done by frequency. They areinitiated by the processor 120 with an admittance read request for agiven socket 102. The FPGA 114 generates the stimulus, processes theresponse, and/or signals the processor 120 that the result is ready tobe read. The processor 120 receives a complex result from the FPGA 114representing the real and/or imaginary part of the admittance.

In example embodiments for current measurements, the measurementprocessor 112 can generate five measurement triggers over 100milliseconds. These triggers can span 6 cycles at 60 Hz or 5 cycles at50 Hz, although other cycle or frequency breakdowns are possible. Thesetriggers can be generated at precise phase shifts from the line powerthat is delivered to each of the sockets 102. The resulting measurementsrepresent the current at those precise phase delays relative to themains power. The measurement processor 112 then computes the averagemagnitude and/or relative phase of the measured current to the mainsvoltage.

Current measurements may be performed in response to a signal triggerrequest from the processor 120. The processor 120 requests a currentmeasurement from the FPGA 114. The FPGA 114 arms and waits for the nextcycle of the mains power to trigger it. Once it receives the trigger,the FPGA 114 makes its five measurements, averages the results, and/orprovides a complex current value representing magnitude and/or phaseback to the processor 120 on completion.

As noted, processor 120 can control user interfaces such as piezoelement 132 and status indicators 134. However, the processor 120 mayalso perform additional roles in the system. For example, the processorcan control the calibration process and the monitoring process for alarmgeneration. The sensor circuits 110 and FPGA 114 can provide real timedata on the status of the loads on each socket 102, while the processor120 can in turn perform calibration and limit checking based on thatdata.

Calibration:

In example embodiments, the power strip 100 can be capable of providingsecurity functions for a number of different types of electricalappliances/devices that may present a wide range of different loads tothe sockets 102. A particular challenge is for the power strip toprovide an effective security function when the socket 102 is connectedto an in-line power supply or power transformer such as USB chargers orpower bricks. These loads present specific challenges in that they canbe disconnected at more than one point (e.g., at the power strip, at thepower supply, or at the device). It is desirable for any disconnect atany of these points to generate an alarm. For example, it is desirablefor the power strip 100 to trigger an alarm if a thief disconnects anelectronic device from a power brick while leaving the power brickconnected to the socket 102. The calibration process described hereincan be employed to learn and/or detect the current and/or admittancecharacteristics of whatever devices are connected to sockets 102, wherethese characteristics may be unique for each device or class of devices.

To support a wide range of devices, a two stage calibration process canbe employed in an example embodiment. This calibration process cangather data on the current and/or admittance characteristics of theconnected device through socket 102 under different conditions, and thecalibration process uses these characteristics to set the alarmthresholds for each device. FIG. 5A shows an example calibration processflow that can be used in an example embodiment.

At step 500, the system measures admittance and current drawcharacteristic data through the socket for a first calibration phase(Phase 1). To perform these measurements, a plurality of stimulationsignals as discussed above can be applied to the socket to trigger aresponse from whatever may be connected to the socket. The responses tothe stimulation signals can be processed to obtain the Phase 1admittance characteristic and current draw characteristic measurements.These measurements can be repeated a plurality of times (e.g., 10times), and the measurements can be averaged together to aggregate themeasurements to single admittance characteristic and current drawcharacteristic values (e.g., Yavg1 and Iavg1). As noted above, thesemeasurements need not be precise computations of admittance and currentin terms of Siemens and Amperes. For example, the measured admittancecharacteristic need only be indicative of the resistive and reactiveportions of a load (or the conductance and susceptance portions of theload) presented to the socket by whatever is connected to the socket. Ifdesired by a practitioner, different weights (W) can be applied todifferent measurements as part of the averaging process. Such a vectorof weights (W) can be stored in and retrieved from memory as needed.Sensor circuit 110 and DSP 114 can be used to support these operations.The Phase 1 measurements can be used by the system to help define thealarm limit(s) that will be used to test for alarm events.

At step 502, the system measures admittance and current drawcharacteristic data through the socket for a second calibration phase(Phase 2). To perform these measurements, the system can once againapply the stimulation signals to the socket to trigger a response fromwhatever may be connected to the socket. The responses to thesestimulation signals can be processed to obtain the Phase 2 admittancecharacteristic and current draw characteristic measurements. Once again,these measurements can be repeated a plurality of times (e.g., 10times), and the measurements can be averaged together to aggregate themeasurements to single admittance characteristic and current drawcharacteristic values (e.g., Yavg2 and Iavg2). Also, as noted, differentweights (W) from a stored weights vector can be applied to differentmeasurements as part of the averaging process. Sensor circuit 110 andDSP 114 can be used to support these operations. The Phase 2measurements can be used by the system, in combination with the Phase 1measurements to help categorize the device connected to the socket.

At step 504, the system categorizes the device connected to the socket102 based on the Phase 1 measurements and the Phase 2 measurements.Based on this categorization, the system can then set one or more alarmlimits for the socket accordingly (step 506).

As noted above, the system preferably supports security functions fordifferent types of devices connected to socket 102.

One type of device that can be connected to the socket is a device thatincludes a cable such as a power cord that plugs into socket 102. Suchdevices typically operate from AC power. In some instances, the cablemay be detachable from the device, but not necessarily. Examples of suchcabled devices include most types of television sets, vacuum cleaners,lamps, etc. Such cabled devices typically have a power switch or thelike that allows power to be turned off for the device. It is preferredthat cabled devices be switched to be in an unpowered state during Phase1 and Phase 2 of the calibration process so that the calibrated powerstrip 100 can be insensitive to variations in characteristics such ascurrent draw that may be experienced by a powered device. Onecomplicating factor that the system can account for with cabled devicesis that some cabled devices exhibit different current drawcharacteristics when in an unpowered state. If the device includescircuitry that allows it to operate in a standby mode while unpowered,the device may still draw current even when turned off. Television setsare a type of cabled device that typically include standby modecircuitry (as are devices such as Blu-Ray players and DVD players).However, for devices that lack such circuitry for a standby mode, therewould be no current draw when turned off. As discussed below, the systemcan be designed to use the Phase 1 and Phase 2 measurements todistinguish between these categories of devices and then tailor thealarm limits accordingly.

Another type of device that can be connected to the socket is a devicethat connects to the socket through an external power transformer suchas a power brick. Such devices typically operate from DC power, and theexternal transformer operates to convert AC power from socket 102 to aDC power for use by the device. For ease of reference, such externalpower transformers will be referred to as power bricks. Power bricks aretypically detachably connectable to the devices they power. Examples ofsuch power bricked devices include most types of laptop computers,tablet computers, smart phones, etc. Power bricks represent a particularchallenge from a security perspective because it is desirable for thesystem to detect both a situation where the power brick and device aretogether removed from the socket 102 and a situation where the device isremoved from the power brick but the power brick remains connected tothe socket 102. Furthermore, different types of power bricks exhibitdifferent electrical characteristics that pose further challenges forthe security function of the socket. For example, a first type of powerbrick (which can be referred to as a regular power brick) will draw somecurrent when connected to socket 102 even if the regular power brick isnot connected to a device; while a second type of power brick (which canbe referred to as a lite power brick) will not draw any appreciablecurrent when connected to socket when no device is connected to the litepower brick. USB chargers for smart phones are often examples of litepower bricks. As discussed below, the system can be designed to use thePhase 1 and Phase 2 measurements to distinguish between these powerbricked categories of devices and then tailor the alarm limitsaccordingly.

During calibration, it is preferred that the devices remained unpowered(e.g., the power switches turned off) for both Phase 1 and Phase 2calibration. For power bricked devices, the Phase 1 calibration occurswhen the power brick is connected to the socket but the device is notconnected to the power brick, and the Phase 2 calibration occurs whenthe power brick is connected to the socket and the (turned off) deviceis connected to the power brick.

FIG. 5B shows an example process flow that can be used for thecategorization and alarm limit setting steps 504 and 506 of FIG. 5A.Different categories of connected devices as discussed above willpresent different admittance and current draw characteristics, and thetwo phases of calibration can be used to distinguish between thesedifferent categories of connected devices. In an example embodiment,processor 120 can perform a variety of comparison and testing operationsto support categorization efforts.

For example, an admittance floor value (Y0) can be used to represent theadmittance of an empty socket. This Y0 value can be stored by the systemand used as a threshold to test for an empty socket condition. Hence,the system can perform a comparison between the Phase 1 measuredadmittance characteristic value (e.g., Yavg1) and the admittance floorvalue (Y0) (step 550). If Yavg1 is greater than Y0, this would indicatethat something is connected to the socket (and the process flow canproceed to step 554). Otherwise, the system will conclude that thesocket is empty, and the process flow can transition to step 552 wherethe socket is categorized as being empty (in which case no alarm limitwould be set). As an example, the comparison that is performed at step550 can compare the square of the absolute value of Yavg1 to the squareof the absolute value of Y0.

A current floor value (I0) can be used to represent no current drawthrough the socket (where some measurement noise tolerance may befactored in). As such, I0 can be conceptually zero plus some tolerancemargin to account for measurement noise. This I0 value can be stored bythe system and used as a threshold to help further categorize aconnected device. At step 554, the system compares the Phase 1 measuredcurrent characteristic value (e.g., Iavg1) with the current floor value(I0). If a cabled and non-bricked device that lacks an active standbymode is connected to the socket, the value of Iavg1 should not begreater than I0. Also, if a lite power brick is connected to the socket,the current draw by the lite power brick will be negligible and shouldalso fall below I0. Hence, the condition where Iavg1 is not greater thanI0 could also indicate the presence of a lite power brick. By contrast,a regular power brick or a cabled device with an active standby modeboth would exhibit an Iavg1 that is greater than I0. Hence, withreference to FIG. 5B, the transition from step 554 to step 556 indicatesthe presence of either a regular power brick or a cabled device with anactive standby mode in the socket, and the transition from step 554 tostep 562 indicates the presence of either a lite power brick or a cableddevice without an active standby mode in the socket. The Phase 2measurements can then be used to resolve further categorization.

At step 556, the system is choosing between candidates of a regularpower brick and a cabled device with an active standby mode. Todistinguish between the two at step 556, the system compares the Phase 2measured current characteristic value (e.g., Iavg2) with the Phase 1measured current characteristic (e.g., IAvg1). If a regular power brickis connected to the socket, the Phase 2 measurements will be made whenthe device is connected to the regular power brick. This deviceconnection will increase the current draw for Phase 2 relative toPhase 1. Hence, an increase in current draw for Phase 2 relative toPhase 1 at step 556 would indicate the presence of a regular powerbrick. In this case, the process flow can transition to step 558 wherethe socket is characterized as being connected to a regular power brick.By contrast, if a cabled device with an active standby mode is connectedto the socket, the Phase 2 current draw should be the same as the Phase1 current draw. Hence, if the current draw for Phase 2 does not increaserelative to that of Phase 1, this would indicate the presence of acabled device with an active standby mode. In this case, the processflow can transition to step 560 where the socket is characterized asbeing connected to a cabled device with an active standby mode. Itshould be understood that the comparison at step 556 could factor insome measurement noise by requiring a distinguishing difference in thePhase 2 current draw to be greater than a defined threshold in order toconclude that the Phase 2 current draw qualifies as an increase from thePhase 1 current draw.

At step 562, the system is choosing between candidates of a lite powerbrick and a cabled device without an active standby mode. To distinguishbetween the two at step 562, the system compares the Phase 2 measuredcurrent characteristic value (e.g., Iavg2) with the Phase 1 measuredcurrent characteristic (e.g., Iavg1). If a lite power brick is connectedto the socket, the Phase 2 measurements will be made when the device isconnected to the lite power brick. This device connection will increasethe current draw for Phase 2 relative to Phase 1. Hence, an increase incurrent draw for Phase 2 relative to Phase 1 at step 562 would indicatethe presence of a lite power brick. In this case, the process flow cantransition to step 564 where the socket is characterized as beingconnected to a lite power brick. By contrast, if a cabled device withoutan active standby mode is connected to the socket, the Phase 2 currentdraw should be the same as the Phase 1 current draw. Hence, if thecurrent draw for Phase 2 does not increase relative to that of Phase 1,this would indicate the presence of a cabled device without an activestandby mode. In this case, the process flow can transition to step 566where the socket is characterized as being connected to a cabled devicewithout an active standby mode. It should be understood that thecomparison at step 562, similarly to the comparison step at 556, couldfactor in some measurement noise by requiring a distinguishingdifference in the Phase 2 current draw to be greater than a definedthreshold in order to conclude that the Phase 2 current draw qualifiesas an increase from the Phase 1 current draw.

After the socket has been categorized, the system can customize one ormore alarm limits accordingly.

At step 570, the system sets alarm limits for a socket categorized asbeing connected to a regular power brick. In this scenario, for anexample embodiment, the system can employ either or both of first andsecond alarm limits that are based on admittance and current drawcharacteristics.

A first alarm limit defined at step 570 can test for whether themeasured admittance characteristic (Y) for the socket has dropped belowthe Phase 1 admittance characteristic value (e.g., Yavg1). If so, thisindicates that the power brick has been removed from the socket, and analarm should be triggered. Any of a number of metrics can be used totest for this condition. For example, this first alarm limit conditioncan include a measurement noise tolerance if desired by a practitionerwhere the decrease in admittance needs to exceed a defined threshold(Ylim or Ylimit). In such an example, the system can trigger an alarm ifthe square of the difference between Y and Yavg1 exceeds Ylim. Inanother example, the first alarm limit can check whether Y is less thanYavg1 (e.g., the system can trigger an alarm if the square of Y is lessthan the square of Yavg1).

A second alarm limit defined at step 570 can test for whether themeasured current characteristic (I) is less than a value above themeasured Phase 1 current characteristic value (e.g., Iavg1) but belowthe measured Phase 2 current characteristic value (e.g., Iavg2). Giventhat the connection of a device to the regular power brick will cause anincrease in the current draw relative to Iavg1, this test can identifysituations where the device has been disconnected from the regular powerbrick but the power brick remains connected to the socket. That isbecause Iavg2 (where the device is connected) is greater than Iavg1(where the regular power brick was connected by the device was not),Iavg1 can be used as a test for indicating disconnection of the deviceindependently of disconnection of the regular power brick. In anexample, this second alarm limit can test whether the newly measuredcurrent characteristic value (I) is less than 110% of the Phase 1current characteristic value (Iavg1). If I is less than 110% of Iavg2,an alarm would trigger because this would indicate that either (1) boththe regular power brick and device were disconnected from the socket (inwhich case the current draw would drop to zero) or (2) only the devicewas disconnected from the regular power brick while the regular powerbrick remained connected to the socket (in which case the current drawwould drop to around Iavg1). While 110% is used as the scalar for Iavg1in this example alarm limit, it should be understood that other scalarscould be used (e.g., 105%, 115%, etc.).

At step 572, the system sets alarm limits for a socket categorized asbeing connected to a cabled device with an active standby mode thatwould draw current even when the device's power switch is turned off. Inthis scenario, for an example embodiment, the system can employ eitheror both of first and second alarm limits that are based on admittanceand current draw characteristics.

A first alarm limit defined at step 572 can be the same alarm limit asdescribed above for the first alarm limit at step 570. That is, thefirst alarm limit for step 572 can test for whether the measuredadmittance characteristic (Y) for the socket has dropped below the Phase1 admittance characteristic value (e.g., Yavg1). If so, this indicatesthat the cabled device has been removed from the socket, and an alarmshould be triggered. As described above, any of a number of metrics canbe used to test for this condition.

A second alarm limit defined at step 572 can test for whether themeasured current characteristic (I) is less than a value slightly belowthe measured Phase 1 current characteristic value (e.g., Iavg1). Giventhat the standby mode will draw largely the same current for both thePhase 1 and Phase 2 calibration measurements, the system can set thealarm limit to be a value slightly below the Phase 1 current drawcharacteristic value (e.g., Iavg1), such as 90% of Iavg1. Thus, if thecabled device is removed from the socket, the newly measured currentdraw characteristic value (I) will fall below 90% of Iavg1, and thesystem can trigger an alarm. Similarly, if the cable is cut or detachedfrom the device, this would also cause I to fall below 90% of Iavg1, andthe system can trigger an alarm. While 90% is used as the scalar forIavg1 in this example alarm limit, it should be understood that otherscalars could be used (e.g., 85%, 95%, etc.).

At step 574, the system sets alarm limits for a socket categorized asbeing connected to a lite power brick. In this scenario, for an exampleembodiment, the system can employ either or both of first and secondalarm limits that are based on admittance and current drawcharacteristics.

A first alarm limit defined at step 574 can be the same alarm limit asdescribed above for the first alarm limit at steps 570 and 572. That is,the first alarm limit for step 574 can test for whether the measuredadmittance characteristic (Y) for the socket has dropped below the Phase1 admittance characteristic value (e.g., Yavg1). If so, this indicatesthat the lite power brick has been removed from the socket, and an alarmshould be triggered. As described above, any of a number of metrics canbe used to test for this condition.

A second alarm limit defined at step 574 can test for whether themeasured current characteristic (I) is less than or equal to the currentfloor (I0). Given that the lite power brick will not draw anyappreciable current when a device is not connected to the lite powerbrick (but will when the device is connected to the power brick), thissecond alarm limit can be used to test for the situation where thedevice has been removed from the lite power brick but the lite powerbrick remains connected to the socket. In this scenario, the newlymeasured I will drop to be the same as or less than I0, and the systemshould trigger an alarm.

At step 576, the system sets alarm limits for a socket categorized asbeing connected to a cabled device without an active standby mode. Inthis scenario, for an example embodiment, the system can employ an alarmlimit that is based on the admittance characteristic. The alarm limitdefined at step 576 can be the same alarm limit as described above forthe first alarm limit at steps 570, 572, and 574. That is, the firstalarm limit for step 576 can test for whether the measured admittancecharacteristic (Y) for the socket has dropped below the Phase 1admittance characteristic value (e.g., Yavg1). If so, this indicatesthat the cabled device has been removed from the socket, and an alarmshould be triggered. As described above, any of a number of metrics canbe used to test for this condition.

In setting these alarm limits, it should be understood that apractitioner may choose to vary the tolerance thresholds and otherconditions based on the determined categorization for the socket. Forexample, the value for Ylim used in the admittance-based alarm limitscan be different values depending on the categorization. Thus, the Ylimused for a cabled device can be a different Ylim than is used for aregular power brick or a lite power brick. Similarly, different Ylimvalues could be used for regular power bricks versus lite power bricks.Similarly, the value for I0 used for a lite power brick could bedifferent than the I0 used during calibration at step 554.

Further still, different categorization process flows could be used ifdesired by a practitioner. For example, the system process flow couldperform the set of condition checks needed for categorization and thenapply Boolean logic to the results to reach conclusions aboutcategorization. Example logic tables for such operations are below:

TABLE 1 Tests and Outcomes Test Outcomes Test A: Is measured Phase 1admittance Condition (1): Test is FALSE characteristic value greaterthan empty Condition (2): Test is TRUE socket admittance value? (e.g.,is Yavg1 > Y0?) Test B: Is measured Phase 1 current Condition (3): Testis FALSE characteristic value greater than Condition (4): Test is TRUEcurrent floor value? (e.g., is Iavg1 > I0?) Test C: Is measured Phase 2current Condition (5): Test is FALSE characteristic value greater thanCondition (6): Test is TRUE measured Phase 1 current characteristicvalue? (e.g., Is Iavg2 > Iavg1?)

TABLE 2 Categories and Conditions Category Conditions Empty SocketCondition (1) Cabled Device with no Active Standby Mode Conditions (2),(3), and (5) Cabled Device with Active Standby Mode Conditions (2), (4),and (5) Regular Power Brick (with Connected Device) Conditions (2), (4),and (6) Lite Power Brick (with Connected Device) Conditions (2), (3),and (6)

Further still, some practitioners may not find it necessary tocategorize on the same categories used by FIG. 5B. As an example, thecategorization process flow of FIG. 6 can be employed to categorizesockets as between empty sockets, sockets connected to cabled devices,and sockets connected to regular power bricks.

Accordingly, the calibration and categorization techniques describedherein permits the system to categorize devices connected to sockets 102into different types of devices/loads, and where the alarm thresholdscan be customized to the particular categorized type of device/loadconnected to a socket 102 while supporting the use of in-line powertransformers and the like. In example embodiments, once the system hasbeen calibrated, the alarm limits for each socket 102 can be stored inNVRAM (non-volatile random-access memory) of the power strip 100 so thesystem can be power cycled without repeating the calibration process.

FIG. 7 shows another example calibration process flow that includes afirst calibration phase 700 and a second calibration phase 702.

The process flow can begin when a user plugs an electrical appliance(which can be referred to as a SKU) into a socket 102. If the SKU is acabled device, the SKU is preferably switched to be in an unpoweredstate during the calibration process so that the calibrated power strip100 can be insensitive to variations in characteristics such as currentdraw that may be experienced by a powered device. Also, if the subjectSKU connects to socket 102 via an in-line power transformer such as acharger or a power brick, this step can include detaching the devicefrom the in-line power transformer such that only the in-line powertransformer is connected to socket 102.

The calibration process then begins, which can be triggered by userinput (e.g., a user using a security fob or the like with interface 130such as an RFID sensor to be authenticated as an authorized user). Aspart of the first calibration phase 700, the power strip 100 can measurethe admittance (Y) and current draw (I) characteristics through thesubject socket 102 a plurality of times (e.g., 10 times), and thesemeasurements can be averaged together. As shown by FIG. 1C, sensorcircuit 110 and FPGA 114 can support these operations.

The process flow can then perform Tests A and B as noted in the tableabove. These tests can be performed by processor 120. Test A can resolvewhether the socket 102 is empty. In the example of FIG. 7, Test B cancategorize as between (1) either a cabled device with an active standbymode or a regular power brick, and (2) a cabled device with no activestandby mode.

For Phase 2 calibration 702, the user can plug a SKU into a power brickconnected to the socket 102 (if applicable). Then, the measurement andaveraging steps are repeated. The processor 120 can then perform Test C,where the outcome of Test C helps categorize as between a cabled devicewith an active standby mode and a regular power brick. The alarm limitscan then be set in response to these categorizations. It is worth notingthat FIG. 7 shows an example calibration process flow where theprocessor need not perform an explicit categorization step, and thecategorization is instead implied by virtue of the logical branchingfrom the outcomes of the various tests.

FIG. 8 shows another example calibration process flow with a focus onuser interface features. At step 800, Phase 1 calibration is initiated.This can be accomplished in any of a number of ways. For example, theuser can use an authorized security fob to be authenticated and initiatethe calibration process. As another example, a calibration command couldbe wirelessly transmitted to the strip 100 via a remote computer systemin response to a request from an authorized user via a user interface.As yet another example, the Phase 1 calibration can be automaticallyinitiated upon detection of a plug event in socket 102 (see Test Adiscussed above).

At step 802, stimulation signals are applied to the socket 102. As notedabove, this step can involve the strip 100 applying multiple admittanceand current draw stimulation signals to the socket 102 to triggervarious electrical responses from whatever is connected to the socket102. At step 804, the electrical responses to these stimulation signalsare measured by sensor circuit 110 and DSP 114 in order to obtain thePhase 1 admittance characteristic value (e.g., Yavg1) and the Phase 1current characteristic value (e.g., Iavg1). At this point, the powerstrip 100 can signal a completion of the Phase 1 calibration to the user(step 806). For example, one or more status indicators 134 can beactivated to signal completion of Phase 1 of calibration.

At this point, if a power brick is connected to the socket 102, the userwill connect the device that is to be secured to the connected powerbrick (step 808). Then, at step 810, Phase 2 calibration is initiated.This can be accomplished in any of a number of ways. For example, theuser can use an authorized security fob to be authenticated and initiatethe Phase 2 calibration process. As another example, a Phase 2calibration command could be wirelessly transmitted to the strip 100 viaa remote computer system in response to a request from an authorizeduser via a user interface. As yet another example, the Phase 2calibration can be automatically initiated upon an arming request froman authorized user.

At this point, stimulation signals are again applied to the socket 102(step 812). These can be the same stimulation signals that were appliedat step 802. At step 814, the electrical responses to these stimulationsignals are measured by sensor circuit 110 and DSP 114 in order toobtain the Phase 2 admittance characteristic value (e.g., Yavg2) and thePhase 2 current characteristic value (e.g., Iavg2).

Then, at step 504, the system attempts to categorize the deviceconnected to the socket based on the measurements from steps 804 and 814as discussed above. If categorization is successful, then theappropriate alarm limit(s) for the socket 102 can be defined at step 506based on the measurements and categorization. If the categorizationfails for some reason, then the process flow can return to step 800.Status indicator(s) 134 can be used to signal whether the calibrationand categorization were successful.

Monitoring:

Once the calibrated alarm limits are set, the system can be armed and itcan then continuously monitor the sockets 102 that had devices presentat the time they were calibrated. An audible and/or visible alarm may begenerated if the alarm conditions set for that socket 102 are met. Thepower strip 100 can be configured to generate alarms on socket fault,system over current, or loss of main power. Each alarm condition can bea unique signature (e.g., a different sound via piezo element 132 or adifferent visual indicator via status indicators 134). The power strip100 can also be controllable to switch between an armed state wheremonitoring to test for security conditions is performed and a disarmedstate where devices can be disconnected from sockets 102 withouttriggering an alarm. As noted above, interface 130, which may take theform of an RFID sensor, can be used to receive user credentials forauthentication to control such arming/disarming operations (as well assilencing alarms if necessary). User authentication via interface 130can also be used to initiate a calibration sequence in the event thesecurity strip is re-merchandised (e.g. new or different appliances areadded to sockets 102). FIG. 9 shows an example process flow forexecution by processor 120 with respect to calibration and monitoringphases of operation.

The calibration process of FIG. 9 can proceed in a fashion similar tothat shown by FIG. 8. The calibration can be performed on asocket-by-socket basis for the power strip 100, and the alarm limits foreach socket can be stored in memory for testing during the monitoringphase to determine whether an alarm should be triggered. If the secondcalibration phase results in successful calibration of the sockets 102,the status indicator 134 can transition to a particular color (e.g.,flashing white) to signal that the strip 100 is calibrated and ready tobe armed. The power strip 100 can be configured to auto-arm at thisstage, or it could require further user input to arm (such as by swipingthe security fob near interface 130). Once armed, the status indicator134 can once again change (e.g., present a solid white color).

Also, if a user wants to change a SKU that is connected to a socket 102,a remerchandising work flow can be followed. To remerchandise a strip100, a user can disarm the strip 100 by swiping his or her security fobnear the interface 130 while the strip 100 is in an armed state. Uponauthentication of the user, the status indicator 134 can transition to anew color (e.g., flashing white) to show the strip 100 as being in adisarmed state. If a device is disconnected from a calibrated socket 102when the strip 100 is disarmed, the system can forget the settings forthat socket 102 in an example embodiment. Also, in an exampleembodiment, once disarmed, the user can hold the security fob nearinterface 130 for a defined duration (e.g., 5 seconds) to put the strip100 into the whitelist/not calibrated state. If the strip 100 isconfigured to detect removals of a SKU when in the disarmed state, thecalibration process can be limited to any sockets 102 that have newlyadded SKUs. For any sockets 102 with unchanged SKUs, the strip 100 canstore a profile of the alarm thresholds for that SKU and re-apply themwhen the strip 102 is re-calibrated without necessarily having to gothrough the full calibration flow for such sockets 102.

When the strip 100 is in an armed state, it can repeatedly check theelectrical characteristics of the calibrated sockets to determinewhether an alarm condition is present. To do so, the strip can apply thestimulation signals discussed above to each calibrated socket 102, andthen measure the electrical responses to these stimulation signals toget the newly measured admittance and current draw characteristic valuesusing the same techniques discussed above for the calibration process.These measured values can be referred to as Y and I values. These Y andI values can then be compared against the defined alarm limits for eachsocket (e.g., see the alarm limits defined at steps 570, 572, 574, and576 of FIG. 5B).

Thus, the table below can show the situations where various categoriesof devices will trigger alarms.

TABLE 3 Alarm Testing Category Alarm Test Alarm Outcome Regular PowerBrick Is I < 1.1*Iavg1? If either is TRUE, then (with Connected Device)OR trigger alarm. Is |Y|{circumflex over ( )}2 < |Yavg1|{circumflex over( )}2? If both are FALSE, then no alarm. Cabled Device with Is I <0.9*Iavg1? If either is TRUE, then Active Standby Mode OR trigger alarm.Is |Y|{circumflex over ( )}2 < |Yavg1|{circumflex over ( )}2? If bothare FALSE, then no alarm. Lite Power Brick (with Is I < I0? If either isTRUE, then Connected Device) OR trigger alarm. Is |Y|{circumflex over( )}2 < |Yavg1|{circumflex over ( )}2? If both are FALSE, then no alarm.Cabled Device with no Is |Y|{circumflex over ( )}2 < |Yavg1|{circumflexover ( )}2? If TRUE, then trigger Active Standby Mode alarm. If FALSE,then no alarm.

It should be understood that these alarm tests are examples, andalternative metrics can be used to test for the respective conditions.For example, the admittance-based alarm tests can include a measurementnoise tolerance if desired by a practitioner where the decrease inadmittance needs to exceed a defined threshold (Ylim or Ylimit). In suchan example, the system can trigger an alarm if the square of thedifference between Y and Yavg1 exceeds Ylim. These Ylim values couldthen vary based on device categorization if desired by a practitioner.

As noted above, if the processor 120 concludes that any of the sockets102 of the strip 100 are in an alarm condition, signals can be providedto piezo element 132 and/or status indicators 134 to signal the alarmcondition to users. Similarly, if the strip 100 supports wirelesscommunications, an alarm notification message can be wirelesslytransmitted to a remote computer system. Furthermore, the alarm signalsand notifications can be socket-specific if desired by a practitioner.

If the strip 100 is in an alarming state, a swipe of a security fob by awhitelisted user can silence the alarm on the strip 100 (e.g., silencepiezo element 132), but the status indicator 134 may continue to flashto signify the alarm state (e.g., flashing red and white). If the strip100 is in a silent alarm mode, the strip 100 can be configured tomaintain the security of unaffected sockets 102 such that the detectionof a subsequent security event at an unaffected socket 102 will triggeran audible alarm to provide a notification that another socket 102 hasbeen compromised. After the strip 100 goes into a silent alarm mode, asubsequent swipe of the security fob by a whitelisted user can triggeran attempt to re-arm the strip. As part of this re-arming, if theaffected socket 102 that was compromised has been re-connected with thesame SKU, then the strip 100 can be configured to self-heal andautomatically re-arm. If the compromised socket 102 is still registeringthe same fault condition, then the strip 100 can remain in the silentalarm mode with the status indicator 134 flashing red and white.

The strip 100 can also provide a process flow for overcurrentsituations. This process flow can provide an overcurrent breaker with astatus indicator that indicates a condition via a state such as flashingblue and an audible signal such as an alert tone of sounds (such as 10double beeps, followed by a brief off period, followed by 10 doublebeeps, etc.) that continues for a specified duration (e.g., 10 minutes).During an overcurrent situation, the strip 100 can power the audiblesignal and status indicators from an internal battery (e.g., battery140). In this overcurrent mode, a user can silence the alarm with aswipe of a security fob near interface 130, but this action would notclear the overcurrent condition. While in this overcurrent mode, thesockets 102 can remain secured such that the unplugging of a SKU wouldtrigger an alarm. To do so, socket power can be shut off, but the sensorcircuits 110 and monitoring circuitry could remain connected to the wallpower (or powered from battery 140 if necessary). Once the overcurrentsituation is cleared, the strip 100 can return to mains power andoperate as normal. The battery 140 can be used to drive the strip 100 inan alarm state for a duration of time deemed necessary for allowing anovercurrent situation to be cleared without an undue risk of batterydrainage that would leave the strip 100 in an unsecured state.Calibration values of sockets 102 can be stored in non-volatile RAM sothat they can be recovered in the event of brief power losses.Furthermore, in the event of mains power loss for an armed strip 100,the loss of mains power can trigger the alarm state (run from battery140).

Additional Example Features:

FIG. 10 shows a general perspective view of an example intelligent powerstrip. The power strip of FIGS. 1A, 1B, and 10 may be made from apolymer material such as a plastic. Components of the power strip may bemolded and assembled together to form the complete power strip. Asnoted, the sockets of the power strip may be molded to fit any number ofoutlet configurations based on the requirements of the power cord forthe electronic appliance. In some embodiments, like those viewed in FIG.1A, the sockets may be a type B socket providing 120V, a type G socketproviding 220V, or a type F socket providing 220V. As voltagerequirements and socket configurations/shapes are usually geographicallydetermined, the top cover of the power strip may be molded toaccommodate the socket configurations/shapes of the location where thepower strip is implemented. The top cover can be further interchangeablewith the bottom cover of the power strip. Therefore, a new or differentsocket configuration top cover may be placed upon an existing powerstrip if the power strip is moved to a region that uses a socketconfiguration.

The top cover of the power strip may also have a user interactionlocation identified on the top cover. The user interaction location insome embodiments may an RFID icon or the like notifying a user where theinternal circuitry for an RFID reader is located. A user using anacceptable RFID device (i.e. badge, card, fob, or the like) may placethe RFID device in proximity to the user access location to facilitateactions of the power strip. As noted above, these actions may includearming or disarming actions of the attached electronic appliances sothat a user may freely attach and remove electronic appliances from thepower strip. A status indicator such as an LED may also be located neara second longitudinal end of the power strip. The LED provides the usera visual status of the power strip. In some embodiments, the LED mayemit a colored illumination based on the status of the power strip.These statuses may include but are not limited to indications or thepower strip being armed, the power strip being disarmed, or the powerstrip acting in an alarming mode.

In the view of FIGS. 1A, 1B, and 10, the top cover can be viewed to havean angled configuration rising from a front side to a rear side of thepower strip. Also on a front side near the second longitudinal end, asound hole may be present for an internal alarm such as a piezo alarm.The internal alarm may have a speaker facing the sound hole to allowsound to travel outside the power strip so that a user may audibly hearthe alarmed state of the power strip.

Viewing the bottom cover of the power strip (see FIG. 1B), a pluralityof fastening points may be seen. These fastening point may be located onthe edges of the bottom cover to attach components of the power striptogether to form the assembly. The plurality of fastening points mayprovide apertures to accept fasteners such as screws or the like tocomplete the assembly. The bottom cover of the power strip may alsocontain a plurality of adhesive areas. Within these area, an adhesive oradhesive pad may be placed on the power strip so that the power stripcan be attached to hidden locations such as a wall or beneath a table ina retail environment in an attempt to obstruct a customer's view of thepower strip.

The first longitudinal end of the power strip may contain a power cordexit. The power cord exit may house a power cord attachable to anoutside socket to provide main power to the power strip. The secondlongitudinal end of the power strip may have an encapsulating design.

Also seen in FIG. 10 is an example expansion module which may be addedand in electronic connection with the power strip. The expansion modulecan support external peripherals and the daisy chaining of multiplepower strips. Circuitry within the power strip itself can be configuredto operate referenced to the main power. An isolated communication bus(see 138 in FIG. 1C) can be included in the design such that anexpansion module can be attached. In example embodiments, use of anisolated communications bus may permit a number of pieces of electronicequipment, such as external peripherals, for example, to be arrangedserially, for example, or in parallel, in a “connected store”architecture. In such an architecture, at least in example embodiments,unauthorized removal of electronic equipment, for example, may bringabout triggering of an alarm, or other form of signal to identify, forexample, to store personnel, that the piece of electronic equipment hasbeen tampered or is the subject of an attempt for unauthorized removal.In some embodiments, the expansion module has the ability to control thepower strip through a UART connection. The expansion module may includea remote RFID module and/or a remote piezo alarm speaker. Additionalembodiments may include network and/or RF mesh network connectivity forhigher level monitoring and/or control of the security strip.

A raised ledge around the power strip may circumnavigate the secondlongitudinal end providing a slight recessed area where the expansionmodule may be positioned to be flush against the second longitudinalend. The second longitudinal end of the power strip may also contain acontact pad. This contact pad may include a plurality of contacts sothat the power strip may connect with the expansion module in someembodiments. The plurality of contacts within the contact pad may bespring contacts which connect to corresponding contacts of the expansionmodule. To facilitate positioning and secure attachment of the expansionmodule to the power strip, a plurality of magnets may be located withinthe interior of the power strip and face the second longitudinal end.When the expansion module is inserted into the recess, the plurality ofmagnets attach to corresponding magnets in the expansion module tosecure connection of the expansion module as well as securing contact ofthe power strip contact pad to the corresponding contacts of theexpansion module.

FIG. 11 shows multiple perspective views of an example expansion module.The expansion module of FIG. 11 may be an assembly that includes a topcover and a bottom cover that are shaped in a manner consistent with thepower strip. Like the power strip, the expansion module may be formedfrom a polymer material such as a plastic. The top cover of theexpansion module may have an angled configuration so that when attachedto the power strip, the assembly of the power strip and the expansionmodule together forms a uniform design. The first end view of theexpansion module shows the expansion module contacts. Similar to thecontact pad of the power strip, the expansion module contacts may be aplurality of contacts such as spring contacts. When the expansion moduleis connected with the power strip, the expansion module contacts contactthe contact pad of the power strip to facilitate electroniccommunication between the two units. In this manner, devices attached tothe expansion module can also be controlled by the alarmingfunctionality of the power strip. The first end view of the expansionmodule shows a tiered view of the surface area of the first end. A risentier provides a majority of the surface area of the first end where alowered edge tier circumnavigates the edge of the first end. When theexpansion module is placed in contact with the power strip, the risentier fits within the recess of the second longitudinal end of the powerstrip while the lowered edge tier contacts the raised edge of the powerstrip. This helps secure the expansion module into the power strip andprovides a visual uniform design. Also located within the expansionmodule are a plurality of expansion module magnets positioned near thefirst end to attached to the plurality of magnets of the power strip.This connection by magnetic force helps secure placement of theexpansion module and the power strip together.

A front side of the expansion module may contain a plurality of frontinput ports. These front input ports are used so that outside componentscan connect to the expansion module to help control and execute thealarming features of both electrical appliances attached to theexpansion module and electronic appliances attached to the power strip.The front input ports may each, in some embodiments, have raised notchesinternal to the port to facilitate the attachment of specific externaldevices. The internal raised notches ensure that only proper electroniccomponents are attached to the expansion module which may communicatewith the power strip based on the connective circuitry between theexpansion module and the power strip.

One front input may provide a connection to a remote interface such asan RFID reader (see RFID port in FIG. 11). In this manner, an RFIDreader can be positioned remotely from the power strip and connect withthe strip via a cable inserted into the RFID port. Thus, the power stripcan be positioned on the floor or underneath a display position such asa table or shelf while the external RFID reader can be positioned in alocation that is more easily accessible by a user. A user using anacceptable RFID device (i.e. badge, card, fob, or the like) may placethe RFID device in proximity to the external RFID reading device tofacilitate actions of the power strip or to control electronicappliances attached to the expansion module. These actions may includearming or disarming actions of the attached electronic appliances sothat a user may freely attach and remove electronic appliances from thepower strip or the expansion module.

Another front input of the expansion module may be an alarming port(e.g., see piezo port in FIG. 11). The alarming port may connect anexternal piezo element such as an alarming buzzer to the expansionmodule. The alarming buzzer may activate when the power strip is in analarming state and produce audible noise to notify the user of thecurrent alarm condition.

A back side of the expansion module may contain a plurality of daisychain ports as well as a power port. The power port may connect a directcurrent to the expansion module to power components, including thoseconnected by the daisy chain ports, such as those connected to the RFIDport and/or alarming port of the expansion module. The expansion modulecontains its own separate power port so that electrical interferencebetween the power strip and the expansion module can be minimized byremoving the need to transmit power through the contacts of both thepower strip and expansion module. The power port in one embodiment isenvisioned to apply direct current into the expansion module, butalternating current power may be providing with rectifying circuitrywithin the expansion module if desired. In example embodiments, a powerbrick with an adapter can be connected to the main power and supplied tothe power port.

The plurality of daisy chain ports allow for additional electronicappliances and even additional power strips to connect to the expansionmodule. In this manner, the original power strip may contain thefunctional alarming conditions for all of the attached electronicappliances, including additional power strips, through the expansionmodule. The daisy chain ports may be RJ11 connectors.

Viewing the bottom cover of the expansion module as shown by FIG. 11, aplurality of expansion fastening points are seen. These expansionfastening points may be located on the edges of the bottom cover toattach the top cover of the expansion module together to form theassembly. The plurality of expansion fastening points may provideapertures to accept fasteners such as screws or the like to complete theassembly. The bottom cover of the expansion module may also contain anexpansion adhesive area. In this area, an adhesive or adhesive pad maybe placed on the expansion module so that the expansion module may beconnectably located near the power strip and attached to a preciselocation such as a wall or beneath a table in a retail environment in anattempt to hide or obstruct a customer's view of the expansion moduleand power strip combination.

FIG. 12 shows a complete view of the power strip attached to anexpansion module with external appliances lined up to be connected tothe front input ports of the expansion module. As stated above, theseexternal appliances may be an alarming buzzer and a RFID reader althoughother components and devices may attached to the these front inputports. The connectors of each the alarming buzzer and the RFID readermay have a unique configuration including traversing channels in boththe latitudinal and longitudinal directions which may fit into theraised notches of their corresponding front input ports to ensure thatthe correct external device is connected to the correct front inputport. Once inserted into the correct front input port, the respectiveconnector may be rotated approximately ninety degrees to lock theconnecter by use of the latitudinal channel to secure the connector tothe front input port. Cords of varying lengths can used to connect theexpansion module to the respective external appliance. The underside ofboth the RFID reader and the alarming buzzer (not shown) may contain anexternal device adhesive area. In this area, an adhesive or adhesive padmay be placed on the external appliance so that the external appliancesmay be located remote from the power strip and expansion moduleassembly. Screw mounts may also be located on these external appliancesto place them in remote locations. Possible remote locations includewalls or on a top surface of a retail table so that store employees andcustomers can both access and be aware of these external appliances andtheir security purpose.

FIG. 13 shows an alternate embodiment of the power strip and expansionmodule. In this example embodiment, the expansion module is configuredas a remote access unit with a different shape and connectionconfiguration than the expansion module of FIGS. 10-12. The nature ofthe interface between the power strip and the expansion module of FIG.13 can be changed relative to the interface used by FIGS. 10-12. Forexample, a latching connector could be used to connect the expansionmodule of FIG. 13 with the power strip. The latching connecter may havea 2×3 pin design and may be a latching Molex connector. A remote accessunit plug may then fit into the latching connector securing the remoteaccess unit to the power strip for electronic communication between theremote access unit and the power strip.

FIG. 14 shows a standalone view of an example remote access unit. Aremote access unit plug may contain the same 2×3 pin design so that itcan be inserted into the latching connector of the power strip. On oneend of the remote access unit plug, a cord connects the remote accessunit plug to a power connector. The cord may vary in length based on theintended use and conditions of the retail environment. The powerconnector may have a stirrup design and connect to either a DC or ACpower source to power the remote access unit. Doing so, electricalinterference between the power strip and the remote access unit isminimized by removing the need to transmit power through the latchedconnector and plug combination. The power port in one embodiment isenvisioned to apply direct current into the remote access unit, butalternating current power may be provided with rectifying circuitrywithin the remote access unit. In an example embodiments, a power brickwith an adapter can be connected to the main power and supplied to thepower connector. However, in other example embodiments, the remoteaccess unit can be powered from the power strip 100 via a power signalpassed through an interface between the remote access unit and powerstrip 100.

On the other side of the remote access unit plug, a second cord can bepresent which connects the plug to the remote access unit. The cord mayvary in length based on the intended use and conditions of the retailenvironment. The remote access unit can terminate in components such asan RFID reader and alarming unit such as noted above in connection withthe expansion module of FIGS. 10-12. Additionally, other connectivityand notification components may be included within this embodiment ofthe remote access unit.

As viewed in FIG. 15, an example alarming/status indicator portion of aremote access unit is shown in greater detail. The remote access unitportion shown by FIG. 15 can include an alarming buzzer such as a piezoalarm. The alarming buzzer connects the remote access unit through aninternal circuit and electrical communication to the piezo alarmfeatures of the power strip. The alarming buzzer may activate in analarming state and produce audible noise to notify the user to a currentalarming condition of at least one electronic appliance connected to thepower strip. For example, during an unauthorized unplugging of anattached electrical appliance from the power strip, the alarming buzzerof the remote access unit may activate so that an audible alarm is heardby store personal indicating a possible issue with the electronicappliance.

The remote access unit portion of FIG. 15 may also include statusindicators that operate as described above for status indicators 134. Inthe example of FIG. 15, the status indicators may take the form of alight ring on a top surface of the remote access unit. The light ringmay take a 360° circular pattern on the top surface. The light ring mayilluminate by a plurality of LEDs in a color scheme based on a state ofthe power strip. If, for example, the color scheme is green, the lightring may indicate that the power strip is deactivated so that a storeemployee can attached or disconnect electronic appliances from the powerstrip without activating an alarm. If, for example, the color scheme iswhite, the light ring may indicate that the power strip is active andarmed so that unauthorized removal of the attached electronic applianceswill cause the power strip to enter and alarming state. Also, forexample, if the color scheme is red, the light ring may indicate thatthe power strip is currently in an alarming state such that there is atleast one issue with either the power strip or the attachment ofelectronic appliances to the power strip. The light ring provides storeemployees and users an easy visual indication as to the status of thepower strip. Due to its attachment remote from the power strip via thecord, the remote access unit may be placed in locations for easy accessand viewing by store employees.

The remote access unit portion shown by FIG. 15 may also have aplurality of socket indicators on the top surface of the remote accessunit. The plurality of socket indicators may illuminate in a colorscheme based on the status of a particular socket of the power strip.For example, in an embodiment, the power strip may have six sockets witheach socket attached to a different electronic appliance. Just as thelight ring visually indicates the status of the overall power strip, theplurality of socket indicators may illuminate to show the socket where aparticular event is occurring. For example, during an alarming event,the color scheme of the light ring of the remote access unit may be red.Additionally, the particular socket indicator of the plurality of socketindicators may also illuminate in a red color to notify a store employeeor user that the electronic appliance attached to that particular socketis the source of the alarming event. The plurality of socket indicatorsfurther allows store employees and users the ability to localize andidentify issues with the power strip during alarming states, disarmingstates, or armed states. Electrical communications between the remoteaccess unit and the power strip are interpreted to illuminate theplurality of socket indicators accordingly.

The remote access unit may also provide connectivity to an outsideremote server. In this regard, the remote access unit may have a networkinterface such as a wireless transceiver to allow the remote access unitto communicate with both a remote server and/or to the electronicappliances attached to the power strip. In example embodiments, theremote access unit can determine the particular type of electronicappliance connected to each socket of the power strip. The remote accessunit may then report through wireless signal transmission back to theremote server the location of each attached electronic appliance in theoverall retail store. If an alarming event was to occur, the remoteaccess unit may communicate the alarming state of both the power stripand the attached electronic appliance to the remote server. In suchinstances, store personnel or security personnel can easily identify thesecurity issue and act accordingly to remedy potential theft situations.

FIG. 16 shows a back view of the remote access unit. The remote accessunit has a circular design and may be an assembly of component partsmanufactured from a polymer material such as plastic. The back surfaceof the remote access unit may have at least two channels crossed withone another. The channels run perpendicular to one another. Each channelhas a depth suitable to fit the cord exiting the middle of the remoteaccess unit. The crossing nature of the channels allows for the cord tobe placed in the appropriate location so that the front view of theremote access unit can be positioned based on the needs and use of thestore employee or user. A plurality of key hole mount may also bepresent on the back surface of the remote access unit. The plurality ofkey hole mounts may affix to a screw to mount the remote access unit ona wall or table. In other embodiments, a remote access unit adhesivearea may be present. In this area, an adhesive or adhesive pad may beplaced on the back surface of the remote access unit so that the remoteaccess unit may be located away from the power strip. Possible remotelocations include walls or on a top surface of a retail table so thatstore employees and customers can be notified of the visual securitysettings of the remote access unit as well as maintain accessibility tothe features of the remote access unit. Placing the remote access unitaway from the power strip also allows the connectivity features of theremote access unit the ability to function without possible inferencegiven off by the power strip's power demands.

FIG. 17 shows another example embodiment where the power strip 100includes a wireless transceiver that provides connectivity for the powerstrip 100 with a remote computer system 100 via a wireless network. Withsuch an embodiment, the computational burden of the calibration and/ormonitoring operations can be shifted to compute resources within aremote computer system 1700 and out of the power strip 100. This canpermit a simplified design for the power strip 100 where the signal datafor the monitored electrical characteristics (e.g., admittance andcurrent draw) are wirelessly communicated from the power strip 100 tothe remote computer system 1700 (see 1702 in FIG. 17). The remotecomputer system 1700 can take the form of a server or othernetwork-accessible service (e.g, a cloud service) that can be leveragedby the power strip 1700 to calibrate and/or monitor the sockets 102.

Also, while the example embodiment discussed above describe the poweredand alarming system for connection to one or more electrical appliancesas being implemented in a power strip, it should be understood that thistechnology could also be implemented in other types of units.

For example, the socket 102 and associated circuitry can be included aspart of a wall outlet or the like to form a “smart” or “intelligent”wall outlet that provides a security function for appliances connectedto the socket. An example is shown by FIG. 18. For example, many walloutlets 1800 feature two sockets 102 in a vertical orientation as shownby the example of FIG. 18, where the sockets are part of an electricalreceptacle 1802 fitted into a recess of a wall. Wiring 1804 then is runto circuitry in the receptacle 1802 to power sockets 102. Some or all ofthe circuitry shown by FIG. 1C can be included in a portion of theoutlet within the receptacle 1802. Similarly, a wireless transceiver canbe included as part of this circuitry to provide wireless connectivitywith remote computer systems that can receive alarms and remotelycontrol the socket(s).

As another example, the secured socket 102 can be different socket typessuch as USB-A sockets, USB-C sockets, RJ-45 sockets, power over Ethernet(PoE) sockets, and others. The calibration and monitoring circuitrydiscussed herein can be connected to any such socket types to provide asecurity function for the subject socket.

Thus, a power and/or alarming security system for electrical appliancesmay provide many benefits. For example, such a system may includemultiple alarm points, such as for power plug removal, power brickremoval, power adapter plug removal, or the like. A power and/oralarming security system for electrical appliances may also provide, forexample, for an easier installation and/or setup, simpler and/orclutter-free solution, merchandising flexibility (e.g., using OEM powercables, etc.), reduced cost solution per position, etc. In someembodiments, an intelligent system may also provide, for example, smartsecurity smart device recognition, self-healing, etc., may detect anumber of types of power loss, relatively quickly disarm and/or managevia RFID key system, or the like. Of course, these are merely examplebenefits of the power and/or alarming security system and otheradvantages may be realized.

While the invention has been described above in relation to its exampleembodiments, various modifications may be made thereto that still fallwithin the invention's scope. Such modifications to the invention willbe recognizable upon review of the teachings herein.

What is claimed is:
 1. An apparatus comprising: a socket configured for detachable electrical connection with a power brick, the power brick configured for detachable electrical connection with an electrical appliance; and a circuit configured to (1) provide power through the socket, and (2) calibrate a security threshold of the socket according to a plurality of calibration phases, (3) monitor, through the socket, an electrical characteristic of a connected power brick and an electrical appliance connected to the power brick, (4) compare the monitored electrical characteristic with the calibrated threshold to determine whether a security condition exists, and (5) generate a signal indicative of the security condition in response to a determination that the security condition exists; wherein the calibration phases comprise (1) a first calibration phase where stimulation signals are applied to the socket and electrical characteristic responses are measured from the socket when the power brick is connected to the socket but an electrical appliance is not connected to the power brick, and (2) a second calibration phase where stimulation signals are applied to the socket and electrical characteristic responses are measured from the socket when the power brick is connected to the socket and the electrical appliance is connected to the power brick.
 2. The apparatus of claim 1 wherein the wherein the monitored electrical characteristic comprises an admittance characteristic of the connected power brick and the electrical appliance connected to the power brick.
 3. The apparatus of claim 2 wherein the wherein the monitored electrical characteristic comprises a current draw characteristic of the connected power brick and the electrical appliance connected to the power brick.
 4. The apparatus of claim 1 wherein the wherein the monitored electrical characteristic comprises a current draw characteristic of the connected power brick and the electrical appliance connected to the power brick.
 5. The apparatus of claim 1 wherein the stimulation signals include a plurality of stimulation signals of different frequencies.
 6. The apparatus of any of claim 1 wherein the circuit comprises a processor configured to perform the compare and generate operations.
 7. The apparatus of claim 1 wherein the circuit comprises a current and admittance sensor circuit configured to sense an admittance and a current draw of the connected power brick and the electrical appliance connected to the power brick to support the calibrate and monitor operations.
 8. The apparatus of claim 1 wherein the circuit is further configured to (1) categorize between a plurality of different types of power bricks as part of the calibration, and (2) customize the security threshold based on the categorized power brick type.
 9. The apparatus of claim 8 wherein the power brick types include a USB charger.
 10. The apparatus of claim 1 wherein the socket comprises a plurality of sockets, each socket connected to the circuit.
 11. The apparatus of claim 10 wherein the circuit is further configured to perform the calibrate operations on a per-socket basis such that security thresholds for the sockets are independently customized.
 12. The apparatus of claim 1 wherein the calibrated security threshold is insensitive to whether the connected electrical appliance is powered.
 13. The apparatus of claim 1 wherein the calibrated security threshold is sensitive to whether the electrical appliance is connected to the power brick.
 14. The apparatus of claim 1 wherein the socket is configured to receive power from an external AC power source.
 15. The apparatus of claim 1 wherein the socket and the circuit are part of a power strip.
 16. The apparatus of claim 1 wherein the socket and the circuit are part of a wall outlet.
 17. A method comprising: connecting a power brick to a socket, wherein the power brick is not connected to an electrical appliance; while the power brick is connected to the socket and the electrical appliance is not connected to the power brick, (1) applying a plurality of stimulation signals to the power brick through the socket, and (2) measuring a plurality of electrical characteristics of the power brick in response to the stimulation signals; connecting the electrical appliance to the power brick; while the power brick is connected to the socket and the electrical appliance is connected to the power brick, (1) applying a plurality of stimulation signals to the power brick and electronic device through the socket, and (2) measuring a plurality of electrical characteristics of the power brick and electronic device in response to the stimulation signals; defining a security threshold based on (1) the measured electrical characteristics of the power brick in response to the stimulation signals and (2) the measured electrical characteristics of the power brick and electronic device in response to the stimulation signals; and testing a security status of the socket based on the defined security threshold.
 18. The method of claim 17 further comprising: in response to the testing, detecting a disconnection between the electrical appliance and the power brick even if the power brick remains connected to the socket.
 19. The method of claim 17 further comprising: in response to the testing, detecting a disconnection between the power brick and the socket.
 20. An apparatus comprising: a socket configured for detachable electrical connection with an electrical appliance; and a circuit configured to (1) provide power to a connected electrical appliance through the socket, (2) determine a categorization type of the connected electrical appliance based on measurements of a plurality of electrical characteristics of the connected electrical appliance, and (3) control a security function for the socket based on the determined categorization type. 